Photosynthesis &
Respiration
What is Photosynthesis?
The process of photosynthesis is a
chemical reaction.
It is the most important
chemical reaction on our planet.
What do plants need for
photosynthesis?
•
•
•
•
Water
Carbon dioxide
Light
chlorophyll
What is the equation for the
chemical reaction of
photosynthesis?
Describe Photosynthesis
• The process of changing light energy to
chemical energy
• Energy stored as sugar
• Occurs in plants and some algae
• Plants need light energy, CO2, and H2O
• Takes place in the chloroplasts, using
chlorophyll, the green pigment in plants
What is it like inside a chloroplast?
• All around the chloroplasts are stacks of
things called thylakoids.
• The part of the chloroplast that is outside
the thylakoids is called the stroma.
• THE CALVIN CYCLE is in the stroma!
What are the two types of reactions
in photosynthesis?
1. The first reaction is called light-dependent
(occurs in the thylakoids)
2. The second reaction is light-independent
(occurs in the stroma)
What do electron carriers do?
• Sunlight makes electrons in the chlorophyll
(located in the thylakoids) very excited!
They are so excited they have to be
carried by a special carrier molecule called
NADP+
• NADP+ carries two electrons at a time.
• It also grabs an H+ ion, and this turns the
NADP+ into NADPH
What does the NADPH do?
• The NADPH carries the very excited highenergy electrons to reactions in the cell.
• These electrons can be used in making
FOOD.
• This is the LIGHT-DEPENDENT Reaction
What is the dreaded Calvin
Cycle?
• The Calvin Cycle uses ATP and NADPH
from light-dependent reactions to produce
high-energy sugars (FOOD)
• The Calvin Cycle is a
LIGHT- INDEPENDENT reaction
What are the products of
photosynthesis?
• High-energy sugars (FOOD)
• oxygen
Why is this important to us?
• We cannot make our own food (glucose,
energy), we must get our food from plants.
• Plants are the first step in the food chain.
• The oxygen released during
photosynthesis is necessary for all living
things.
Quiz
1) Describe what it’s like inside a chloroplast.
2) Why does Hamel say that photosynthesis is
one of the most important chemical reactions
on Earth?
3) What happens during the Calvin Cycle?
4) What are the products of photosynthesis?
5) What is needed for photosynthesis?
6) What happens to electrons during
photosynthesis?
7) Which happens first, light-dependent reactions
or light-independent ones?
8) What does NADP+ do?
What is Cellular Respiration?
• Once the energy that was in sunlight is
changed into chemical energy by
photosynthesis, an organism has to
transform the chemical energy into a form
that can be used by the organism.
• Cellular respiration is the process that
releases energy by breaking down food
molecules in the presence of oxygen.
Describe Cellular Respiration
• The breakdown of glucose molecules to
release energy
• Takes place in all living things
• Is a step by step process
Where does cellular respiration
happen?
• In the mitochondria of living
things.
What is the chemical equation
for cellular respiration?
Diagram of the Process
Occurs
across
Cristae
Occurs in
Cytoplasm
Occurs in
Matrix
What are the Stages of
Cellular Respiration?
• Glycolysis
• The Krebs Cycle
• The Electron Transport Chain
Anaerobic Processes
• No oxygen is
required for these
processes.
• Includes
glycolysis, the
breakdown of
glucose, and
fermentation.
• Some bacteria
and yeast are
examples of
anaerobes.
http://www.biol.vt.edu/research/images/C._perfringens_in_mac._jpg.jpg
http://www.utoronto.ca/greenblattlab/images/a/yeast%201.jpg
Glycolysis
• Occurs in the
cytoplasm.
• Breaks down glucose
into 2 molecules of
pyruvate
• 2 ATP molecules are
formed.
 The series of reactions
in which pyruvate is
broken down into
carbon dioxide is called
the Krebs cycle.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/enyld1.gif
Yikes! There’s another cycle?
• Yes. The Krebs cycle.
• The Krebs cycle is where energy is
released. Kind of like the Calvin
Cycle in reverse…
What happens during the Krebs
cycle?
• Energy is freed from the
chemical bonds. The excited
electrons are FREEE!
• The electrons make ATP.
• Carbon dioxide is released.
You get rid of it by exhaling…
Where do the electrons go?
• On the train!
• The electrons get to ride the
electron transport train, the Final
step in the breakdown of glucose.
• Point at which ATP is produced
What happens to ADP on the train?
• Ions rush back and forth and spin
the ADP in circles.
• This creates enough energy to
produce three molecules of ATP
per molecule of ADP.
• ATP and ADP are special
molecules that store energy
Quiz
1. Where does cellular respiration take
place?
2. What is the chemical equation for
cellular respiration?
3. What are the products of cellular
respiration?
4. What is the Krebs Cycle?
5. What happens during the Krebs
Cycle?
6. What happens to electrons during
cellular respiration?
7. How much ATP is produced from one
molecule of ADP?
Complementary processes
• Photosynthesis is an
important part of the
carbon cycle.
• The processes of
photosynthesis and
cellular respiration are
complementary
processes, meaning
they work together to
benefit living
organisms.
Plants and animals contribute…
• Autotrophs, such as plants, produce
glucose using the carbon in carbon
dioxide.
• Both autotrophs and heterotrophs, such as
grasshoppers that eat plants, use those
carbohydrates in cellular respiration.
• Respiration, in turn, produces carbon
dioxide.
Energy renewal
• Energy captured from
sunlight by
photosynthetic
organisms is used
and released in the
cellular respiration of
living things.
• The energy that living
things use, must
continually be
renewed through
photosynthesis.
• Now create a diagram, that represents the
relationship between photosynthesis and
cellular respiration (the carbon cycle).
• Diagram must include at least one
autotroph and one heterotroph.
• Illustrate and label the stages.
• Title: Photosynthesis/Respiration